This proposal builds upon the strengths of two successful NCVDG awards to the University of Washington since 1987. The overall objective of this program is to develop and evaluate combination immunization strategies that are broadly protective against blood-borne and mucosal infection by primary isolates of HIV-1. The central hypothesis of this program is two-fold: (1) protection against HIV infection is immune- mediated, and (2) protection can be achieved by combination immunization with recombinant vaccines. These hypotheses are supported by work accomplished in the present NCVDG demonstrating that a combination immunization regimen with recombinant live vector priming followed by recombinant protein immunogen boosting protected macaques against intravenous and intrarectal infection by pathogenic uncloned virus, SIVmne. We recently extended these observations to include protection against SHIV IIIB in macaques. The goal of this proposal is to develop novel combination immunization strategies that will result in protection against primary isolates of HIV-1 in relevant non-human primate models. The Specific Aims are: (1) To refine a combination immunization approach with proven efficacy in the SIVmne and Shiv IIIB models and to determine the immune mechanisms and the limits of protection against SHIV with envelope from primary isolates of HIV-1 (Project/HU); (2) To generate broadly protective immune responses by "quasispecies" vaccination, using a combination of DNA and recombinant immunogen immunization strategies (Project 2/Haigwood); (3) To examine combination systemic and/or mucosal immunization approaches to elicit immunity against mucosal infection (Project 3/Bosch); and (4) To examine the role of T-cell immunity in protection as well as combination vaccination strategies designed to augment T-cell responses (Project 4/Greenberg). These efforts will be supported by three scientific Cores to develop chimeric Shiv representing the diversity of primary HIV-1 isolates (Core B/Mullins), to develop and maintain non-human primate resources (Core A/Anderson) as well as virological/serological techniques (Core C/ Agy) necessary for the preclinical evaluation of candidate HIV-1 vaccines. Results from this program project will contribute directly to current and future clinical development of AIDS vaccines and enhance our basic understanding of the protective immunity against primate lentiviruses.